Friend of mine has got problem with his new desktop (XP SP2) , when he starts the PC it boots normally till it reaches where it shows windows XP logo then the screen gets blank (i.e he can not see the login name for users).
What he used to do: is press the sleep button on the keyboard, then after that press the hardware switch on/off button (not the reset button) on the tower of the hard box.
After pressing switch on/off button, he gets directly (pay attention to this) to the login screen where he can see the usernames for all users.
He has to do this procedure every time he would like to boot the desktop
VGA is NiVida with dual outputs, similar to below image
go into the power management settings and turn off hibernation, sleep, and anything else that turns stuff off. Set everything to never. Also check the bios for anything that might put the computer into sleep mode.